Tapered roller wheel bearing assembly

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0032179 filed in the Korean Intellectual Property Office on Mar. 26, 2013, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a tapered roller wheel bearing assembly. More particularly, the present invention relates to a tapered roller wheel bearing assembly having a second undercut for dispersing stress concentrated on a first undercut formed at a flange base portion.

(b) Description of the Related Art

Generally, a bearing is disposed between a rotating element and a non-rotating element so as to smooth rotation of the rotating element. Various types of bearings such as a ball bearing, a tapered roller bearing, needle bearing, and so on are currently used.

A wheel bearing is one type of such bearings, and rotatably connects a wheel that is the rotating element to a vehicle body that is non-rotating element. The wheel bearing includes an inner ring (and/or a hub) connected to one of a wheel or a vehicle body, an outer ring connected to the other of the wheel or the vehicle body, and rolling elements disposed between the outer ring and the inner ring.

Balls or tapered rollers are used as the rolling elements of the wheel bearing. Wheel bearings using balls are applied to small vehicles, and wheel bearings using tapered rollers are applied to large vehicles such as buses, trucks and so on.

A conventional tapered roller wheel bearing assembly is illustrated in <figref idref="DRAWINGS">FIG. 1</figref> to <figref idref="DRAWINGS">FIG. 3</figref>.

As shown in <figref idref="DRAWINGS">FIG. 1</figref> to <figref idref="DRAWINGS">FIG. 3</figref>, the conventional tapered roller wheel bearing assembly <b>10</b> includes a hub <b>20</b>, an inner ring <b>60</b>, an outer ring <b>30</b>, and first and second tapered rollers <b>40</b> and <b>50</b>.

A hub flange <b>23</b> for mounting a wheel is formed at a side portion of the hub <b>20</b> and a stepped portion <b>26</b> is formed on the other side portion of the hub <b>20</b>. In addition, a hub raceway <b>25</b> is formed on an exterior circumference of the hub <b>20</b> between the hub flange <b>23</b> and the stepped portion <b>26</b>, and a flange base <b>24</b> is formed at a connecting portion of the hub raceway <b>25</b> and the hub flange <b>23</b>. Typically, a cross-section of the flange base <b>24</b> is formed in a curved fashion. A bolt hole <b>29</b> is formed at a radial outer portion of the hub flange <b>23</b> and a bolt is inserted in the bolt hole <b>29</b> such that the wheel is mounted on the hub flange <b>23</b>. In addition, a pilot <b>22</b> for supporting the wheel is protruded from a side surface of the hub <b>20</b> in an axial direction.

The inner ring <b>60</b> is press-fitted onto the stepped portion <b>26</b> and an inner raceway <b>62</b> is formed on an exterior circumference of the inner ring <b>60</b>. After the inner ring <b>60</b> is press-fitted onto the stepped portion <b>26</b>, an end portion <b>27</b> of the hub <b>20</b> is bent radially outwardly so as to catch the inner ring <b>60</b>. Thereby, preload is applied to the first and second tapered rollers <b>40</b> and <b>50</b>.

The outer ring <b>30</b> is spaced radially outwardly from the hub <b>20</b> and the inner ring <b>60</b> and encloses the hub <b>20</b> and the inner ring <b>60</b>. First and second outer raceways <b>32</b> and <b>34</b> corresponding to the hub raceway <b>25</b> and the inner raceway <b>62</b> are formed on an interior circumference of the outer ring <b>30</b>.

A plurality of first tapered rollers <b>40</b> is mounted between the hub raceway <b>25</b> and the first outer raceway <b>32</b> in a state of being mounted in a first retainer <b>42</b>, and a plurality of second tapered rollers <b>50</b> is mounted between the inner raceway <b>62</b> and the second outer raceway <b>34</b> in a state of being mounted in a second retainer <b>52</b>.

Meanwhile, in a case that the first and second tapered rollers <b>40</b> and <b>50</b> are mounted on the hub <b>20</b> and the inner ring <b>60</b>, the hub raceway <b>25</b> and protruded portions positioned at both end portions of the hub raceway <b>25</b>, the inner raceway <b>62</b>, and protruded portions positioned at both end portions of the inner raceway <b>25</b> that may contact with the first and second tapered rollers <b>40</b> and <b>50</b> should be machined precisely. Generally, although edges of the tapered rollers are arched, raceways are not machined in an arched fashion but are machined in a straight fashion due to characteristics of machining. In addition, since machined surfaces of each raceway and machined surfaces of protruded portions positioned at the both end portions of each raceway form angles, an edge portion at which the machined surfaces are joined is difficult to be machined. To solve such problems, an undercut is formed at the edge portion at which the machined surfaces are joined. That is, a groove is formed in advance circumferentially at the edge portion at which the machined surfaces are joined for ease of machining.

However, if the undercut is formed for ease of machining, the wheel bearing assembly becomes weak against impact. Particularly, if instant impact or strong impact is applied through the hub flange <b>23</b>, as shown in <figref idref="DRAWINGS">FIG. 4</figref>, stress is concentrated on the undercut <b>28</b> formed at the flange base <b>24</b> and crack may occur around the undercut <b>28</b> or the hub <b>20</b> may be damaged due to concentration of stress. Since the undercut <b>28</b> should be formed for ease of machining, means for dispersing stress that may be concentrated on the undercut <b>28</b> is necessary.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide a tapered roller wheel bearing assembly having advantages of dispersing stress by forming an additional undercut near an undercut for machining a hub raceway.

A tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention may include: a hub provided with a hub flange for mounting a wheel formed radial outwardly at an end portion thereof, a stepped portion formed at an exterior circumference of the other end portion thereof, and a hub raceway formed at an exterior circumference between the hub flange and the stepped portion; an inner ring press-fitted on the stepped portion of the hub and provided with an inner raceway formed at an exterior circumference thereof; an outer ring enclosing the hub and the inner ring and provided with first and second outer raceways corresponding to the hub raceway and the inner raceway and formed at an interior circumference thereof; a first tapered roller disposed between the hub raceway and the first outer raceway and allowing a relative rotation of the hub or the inner ring and the outer ring; and a second tapered roller disposed between the inner raceway and the second outer raceway and allowing the relative rotation of the hub or the inner ring and the outer ring, wherein a flange base is formed between the hub flange and the hub raceway and a first undercut for grinding the hub raceway is formed at the flange base, and wherein a second undercut for dispersing stress concentrated on the first undercut is further formed at the flange base.

The second undercut may be formed at a radial outside of the first undercut and spaced apart from the first undercut by a predetermined distance.

Size of the second undercut may be larger than that of the first undercut.

A pilot for supporting the wheel may be protruded in an axial direction at a side surface of the hub and the second undercut may be formed at the same radial position as the pilot substantially.

A first sealing member for preventing inflow of foreign material may be mounted between the hub flange and an end of the outer ring, and a second sealing member for preventing inflow of foreign material may be mounted between an interior circumference of the other end portion of the outer ring and an exterior circumference of the inner ring.

The second undercut may be positioned at a radial inside from the first sealing member.

A tapered roller wheel bearing assembly according to another exemplary embodiment of the present invention may include: a hub provided with a hub flange for mounting a wheel formed radial outwardly at an end portion thereof and a hub raceway formed at a side portion close to the hub flange; an outer ring enclosing the hub and provided with an outer raceway corresponding to the hub raceway on an interior circumference thereof; and a tapered roller disposed between the hub raceway and the outer raceway and allowing a relative rotation of the hub and the outer ring, wherein a flange base is formed between the hub flange and the hub raceway and a first undercut for grinding the hub raceway is formed at the flange base, and wherein a second undercut for dispersing stress concentrated on the first undercut is further formed at the flange base.

The second undercut may be formed at a radial outside of the first undercut and spaced apart from the first undercut by a predetermined distance.

Size of the second undercut may be larger than that of the first undercut.

A pilot for supporting the wheel may be protruded in an axial direction at a side surface of the hub and the second undercut may be formed at the same radial position as the pilot substantially.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> is a cross-sectional view of a conventional tapered roller wheel bearing assembly.

<figref idref="DRAWINGS">FIG. 2</figref> is a cross-sectional view of a hub used in a conventional tapered roller wheel bearing assembly.

<figref idref="DRAWINGS">FIG. 3</figref> is a partial perspective view of a hub used in a conventional tapered roller wheel bearing assembly.

<figref idref="DRAWINGS">FIG. 4</figref> illustrates stress distribution when impact is applied to a hub used in a conventional tapered roller wheel bearing assembly.

<figref idref="DRAWINGS">FIG. 5</figref> is a cross-sectional view of a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention.

<figref idref="DRAWINGS">FIG. 6</figref> is a cross-sectional view of a hub used in a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention.

<figref idref="DRAWINGS">FIG. 7</figref> is a partial perspective view of a hub used in a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention.

<figref idref="DRAWINGS">FIG. 8</figref> illustrates stress distribution when impact is applied to a hub used in a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

<figref idref="DRAWINGS">FIG. 5</figref> is a cross-sectional view of a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention, <figref idref="DRAWINGS">FIG. 6</figref> is a cross-sectional view of a hub used in a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention, and <figref idref="DRAWINGS">FIG. 7</figref> is a partial perspective view of a hub used in a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention.

A tapered roller wheel bearing assembly <b>100</b> illustrated in <figref idref="DRAWINGS">FIG. 5</figref> to <figref idref="DRAWINGS">FIG. 7</figref>, for better comprehension and ease of description, exemplifies any one tapered roller wheel bearing assembly among various tapered roller wheel bearing assemblies. Therefore, it is to be understood that spirit of the present invention is not limited to the tapered roller wheel bearing assembly <b>100</b> exemplified in this specification but is applied to various tapered roller wheel bearing assemblies. It is further to be understood that the spirit of the present invention can be applied to any bearing including a rotating ring (a ring that can be rotatable), a non-rotating ring (a ring that cannot be rotatable), and a plurality of tapered rollers interposed between the rotating ring and the non-rotating ring. In addition, the tapered roller wheel bearing assembly illustrated in <figref idref="DRAWINGS">FIG. 5</figref> to <figref idref="DRAWINGS">FIG. 7</figref> is a tapered roller wheel bearing assembly for a driving wheel. Since a tapered roller wheel bearing assembly for a driven wheel is similar to the tapered roller wheel bearing assembly for the driving wheel, however, it is to be understood that the spirit of the present invention is not limited to the tapered roller wheel bearing assembly for the driving wheel but is applied to the tapered roller wheel bearing assembly for the driven wheel.

In addition, for ease of description, <figref idref="DRAWINGS">FIG. 5</figref> to <figref idref="DRAWINGS">FIG. 7</figref> exemplify that the spirit of the present invention is applied to a ‘3^rd-generation tapered roller wheel bearing’, but is not limited thereto. That is, the spirit of the present invention can be applied to tapered roller wheel bearings of all the generations.

Meanwhile, for ease of description, a region close to a wheel (not shown) is called an outboard and a region far from the wheel is called an inboard in all the constituent elements included in the tapered roller wheel bearing assembly.

As shown in <figref idref="DRAWINGS">FIG. 5</figref> to <figref idref="DRAWINGS">FIG. 7</figref>, the tapered roller wheel bearing assembly <b>100</b> according to an exemplary embodiment of the present invention includes a hub <b>110</b>, an inner ring <b>130</b>, an outer ring <b>160</b>, and first and second tapered rollers <b>140</b> and <b>150</b>. It is shown in this specification, but is not limited to, that two rows <b>2</b> tapered rollers are used. The number of rows of the tapered rollers may be suitably chosen by a person of an ordinary skill in the art. Typically, the first and second tapered rollers <b>140</b> and <b>150</b> may be formed by fitting a plurality of tapered rollers into first and second retainers <b>142</b> and <b>152</b> made of resin material.

The hub <b>110</b> has a cylindrical shape and the wheel of a vehicle is coupled to an outboard end portion of the hub <b>110</b>. For this purpose, a hub flange <b>114</b> extending radially outwardly and a pilot <b>112</b> protruding to an outboard side along a rotation axis are formed at the outboard end portion of the hub <b>110</b>. A bolt hole is bored at the hub flange <b>114</b> such that the wheel of the vehicle is coupled to the hub <b>110</b> through coupling means such as a bolt, and the pilot <b>112</b> guides and supports the wheel when the wheel is coupled to the hub <b>110</b>. In addition, a stepped portion <b>116</b> is formed on an inboard end portion of the hub <b>110</b>, and an end portion <b>118</b> is extended from the stepped portion <b>116</b>. The end portion <b>118</b> is extended straightly to the rotation axis direction before orbital forming, but is deformed plastically in a radial outward direction after the orbital forming. A hub raceway <b>120</b> is formed on an exterior circumference between the stepped portion <b>116</b> of the hub <b>110</b> and the hub flange <b>114</b>, and a flange base <b>122</b> is formed between the hub flange <b>114</b> and the hub raceway <b>120</b>.

The inner ring <b>130</b> is press-fitted on the stepped portion <b>116</b> of the hub <b>110</b>, and an inner raceway <b>132</b> is formed on an exterior circumference of the inner ring <b>130</b>. The inner ring <b>130</b> is mounted on the hub <b>110</b> through orbital forming of the end portion <b>118</b> of the hub <b>110</b>. In this process, preload may be applied to the first and second tapered rollers <b>140</b> and <b>150</b>. It is exemplified in this specification that the inner ring <b>130</b> is mounted on the hub <b>110</b> through the orbital forming, but the inner ring <b>130</b> may be mounted on the hub <b>110</b> by a bolt.

The outer ring <b>160</b> is positioned radially outwardly from the hub <b>110</b> and encloses the hub <b>110</b> and the inner ring <b>130</b>. First and second outer raceways <b>162</b> and <b>164</b> corresponding to the hub raceway <b>120</b> and the inner raceway <b>132</b> are formed on an interior circumference of the outer ring <b>160</b>, and a part of exterior circumference of the outer ring <b>160</b> protrudes radially outwardly to form a flange. A bolt hole (not shown) is bored at the flange such that the outer ring <b>160</b> is coupled to a vehicle body (for example, a knuckle) through coupling means such as a bolt.

The first tapered roller <b>140</b> is disposed between the hub raceway <b>120</b> and the first outer raceway <b>162</b>. The second tapered roller <b>150</b> is disposed between the inner raceway <b>132</b> and the second outer raceway <b>164</b>. The first and second tapered rollers <b>140</b> and <b>150</b> allow relative rotation of the hub <b>110</b> and the inner ring <b>130</b>, and the outer ring <b>160</b>.

In addition, a first sealing member <b>170</b> is mounted between the hub flange <b>114</b> and an outboard end of the outer ring <b>160</b> so as to prevent inflow of foreign material such as dust and moisture, and a second sealing member <b>172</b> is mounted between an inboard end of the outer ring <b>160</b> and the exterior circumference of the inner ring <b>130</b> so as to prevent inflow of foreign material such as dust and moisture. The first and second sealing members <b>170</b> and <b>172</b> may be sealing members of the same type or different type.

Meanwhile, it is exemplified in this specification that the tapered roller wheel bearing assembly <b>100</b> includes the hub <b>110</b> connected to the wheel and rotating and the outer ring <b>160</b> connected and fixed to the vehicle body, but the tapered roller wheel bearing assembly is not limited thereto. That is, the hub <b>110</b> may be connected to the vehicle body and the outer ring <b>160</b> is connected to the wheel and rotates.

In addition, the tapered roller wheel bearing assembly <b>100</b> according to the exemplary embodiment of the present invention uses the tapered rollers <b>140</b> and <b>150</b> as rolling elements. Therefore, an undercut for machining the raceways is necessary. For these purposes, a first undercut <b>124</b> is formed on the flange base <b>122</b> connected to the hub raceway <b>120</b>. That is, a side edge of the first tapered roller <b>140</b> is inserted in the first undercut <b>124</b>. However, if external impact is applied to the hub flange <b>114</b>, stress is concentrated on the first undercut <b>124</b>. Therefore, crack may occur or the tapered roller wheel bearing assembly <b>100</b> may be damaged. Therefore, a second undercut <b>126</b> is formed near the first undercut <b>124</b> so as to disperse stress according to the exemplary embodiment of the present invention. The second undercut <b>126</b> is formed on the flange base <b>122</b> and is spaced apart from the first undercut <b>124</b> radially outwardly by a predetermined distance. If the second undercut <b>126</b> is formed far from the first undercut <b>124</b>, stress cannot be dispersed. In contrast, if the second undercut <b>126</b> is formed very close to the first undercut <b>124</b>, the first and second undercuts <b>124</b> and <b>126</b> are operated as one groove and stress may be concentrated thereon. Therefore, a distance between the first undercut <b>124</b> and the second undercut <b>126</b> is very important to achieve spirit of the present invention, and may be set depending on size of the tapered roller wheel bearing assembly <b>100</b> as a suitable value by a person of an ordinary skill in the art. For example, the distance between the first undercut <b>124</b> and the second undercut <b>126</b> may be, but is not limited to, about 0.3 cm-2 cm.

In addition, size of the second undercut <b>126</b> may be larger than that of the first undercut <b>124</b> in order to heighten stress dispersion effect. Herein, the size of the undercut may be depth or radius of the undercut. Further, the second undercut <b>126</b> may be formed at the same radial position as the pilot <b>112</b>, and may be formed at a radial inner position than the first sealing member <b>170</b>.

The second undercut <b>126</b> disperses stress concentrated on the first undercut <b>124</b>.

A cross-sectional shape of the second undercut <b>126</b> has a smooth curved line.

<figref idref="DRAWINGS">FIG. 8</figref> illustrates stress distribution when impact is applied to a hub used in a tapered roller wheel bearing assembly according to an exemplary embodiment of the present invention.

Since the second undercut <b>126</b> is positioned near the first undercut <b>124</b>, as shown in <figref idref="DRAWINGS">FIG. 8</figref>, stress concentrated on the first undercut <b>124</b> is disposed to the first and second undercuts <b>124</b> and <b>126</b>. If maximum stress applied to the first and second undercuts <b>124</b> and <b>126</b> is calculated, maximum stress applied to the first undercut <b>124</b> is larger than that applied to the second undercut <b>126</b>. However, the maximum stress applied to the first undercut <b>124</b> is reduced by more than 10%, compared with a conventional taper bearing. That is, since part of stress concentrated on the first undercut <b>124</b> is absorbed by the second undercut <b>126</b>, strength of stress concentrated on the first undercut <b>124</b> is reduced. Therefore, possibilities of crack occurrence around the first undercut <b>124</b> may be lowered and possibilities of breakdown of the tapered roller wheel bearing assembly <b>100</b> may also be lowered. Resultantly, the tapered roller wheel bearing assembly <b>100</b> may endure stronger impact.

As described above, stress may be dispersed by forming an additional undercut near an undercut for machining a hub raceway according to an exemplary embodiment of the present invention. Therefore, the tapered roller wheel bearing assembly may endure stronger impact.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.